The present invention relates to a meter-recorder for measuring output power of a solar cell over a long term and recording the measured data.
Microwave repeater stations are normally located at mountain tops or high lands for securing a line-of-sight between the respective stations. Such locations are usually very far from a power line of a commercial power source, and often encounter difficulties in power supply. Accordingly, with regard to the communication apparatuses to be installed at such remote places, it has been strongly required to minimize power consumption so that the power may be supplied by a solar cell arrangement. While a power supply employing a solar cell arrangement is constructed of a number of solar cells and a storage battery, the output power of the solar cell arrangement, i.e., the magnitude of the effective light reception area of the solar cell arrangement must be determined depending upon an average sunshine time and insolation intensity over a year or a comparable period of time in the neighborhood of the communication station site and upon power consumption of the entire communication apparatuses at the station. In other words, if the effective light reception area of the solar cell arrangement is made large enough, the solar cell can supply the required power even if the sunshine time and the insolation intensity are insufficient, but the manufacturing cost of the solar cell arrangement becomes extremely high. On the contrary, if the effective light reception area of the solar cell arrangement is made too small, the power supply to the communication apparatuses becomes insufficient when the sunshine time is reduced, driving the communication apparatuses out of operation. Accordingly, it is necessary to acquire data on the sunshine condition in the neighborhood of the communication station site over a long term and to preset the capacities of the solar cell and the storage battery at optimum values on the basis of the acquired data.
Measurement of output power of a solar cell is carried out in terms of an accumulated value for one day of solar energy irradiating a horizontal area of 1 square-centimeter (cm.sup.2) at a measuring point (Langley value). Such type of apparatus is described, for example, in a catalogue titled "Solar Cell Test Data Processing System" distributed from SPECTROLAB, Sylmar, California, U.S.A. This system comprises a data acquisition section for acquiring data such as output power of a solar cell of the like, a data processing section containing a computer for processing the acquired data and a printer or the like for recording the processed data. While this system can assure a high precision of measurement and provide readily available data, it requires a commercial power supply because of large power consumption, so that it is not suitable as a measuring apparatus to be operated at remote places where such a commercial power supply is not available. In order to overcome this difficulty, various methods have been proposed such as modifying the printer into an impact type to reduce power consumption, recording an output voltage of a solar sensor directly on a recording web in ink, or recording it on a black scratch film with a diamond stylus. However, the recording on a web by an impact shot or in ink is not suitable for long-term measurement and recording because of the need for supplement of a new inked ribbon and ink. Furthermore, in the apparatus for directly recording an output voltage of a solar sensor, a graph showing the insolation intensity and recorded on the recording web cannot be utilized directly but it must be converted into Langley values.